Recently, electric vehicles driven with electricity as a power source, compared with vehicles driven with an engine, have been developed due to depletion of oil fuels, growing environmental restrictions, and for the purpose of enhancing fuel efficiency.
Thus, vehicle components using an electric motor have been researched, and development of electro-mechanical brake (EMB) technologies based on a braking scheme using a motor and a mechanical element have been ongoing.
Brake-by-wire, a higher concept, includes an electronic pedal, a wiring, a controller, and an EMB and is advantageous in that it can be configured with a smaller amount of components and a braking distance can be reduced through fast braking responsiveness, compared with an existing hydraulic brake system composed of a pedal, a hydraulic booster, a master cylinder, a hydraulic pipe, and a hydraulic caliper.
The existing hydraulic brake obtains clamping force required for braking by amplifying force.
First, force exerted as a driver steps on a pedal is amplified based on the principle of the lever, and secondly, force is additionally amplified by a hydraulic booster by using vacuum pressure generated in an intake stroke of an engine.
The amplified force is converted into hydraulic pressure in a master cylinder, and the hydraulic pressure is transmitted to a slave cylinder of a caliper.
The same hydraulic pressure is formed in the master cylinder and the slave cylinder of the caliper, and in the slaver cylinder of the caliper having a greater diameter, force corresponding to a ratio of a sectional area to that of the master cylinder is additionally amplified based on the Pascal's principle.
The force amplified three times pushes the piston to act as clamping force on a disk.
An EMB also requires a high output motor that may be able to provide high torque to provide strong clamping force such as that of a hydraulic brake.
A wedge-type EMB utilizing a self-servo effect of a mechanism, while using a low output motor has also been proposed.
As for implementation of a wear compensation function, in the case of an existing hydraulic brake, an oil seal positioned between a hydraulic piston and a cylinder serves to uniformly maintain a distance between a disk and a brake pad regardless of wear of the brake pad.
In contrast, in the case of EMB, since an oil seal is not present, a high-priced displacement sensor, or the like, which may be able to uniformly maintain a distance between a disk and a brake pad is installed to perform a wear compensation function, increasing costs of products.